4 - Physical oceanography of Campos Basin continental slope and ocean region

Abstract

Ocean circulation on the continental slope and São Paulo Plateau in the Campos Basin is governed by the so-called “Brazil Current System” which is formed by the Brazil Current (BC), the Intermediate Western Boundary Current (IWBC) and by the meanders and eddies associated with both flows. The water column of this current system is formed by a stacking of water masses, whose depths and interfaces vary due to the baroclinic adjustment of these flows. A multiparametric, physical and hydrochemical analysis of water masses, unprecedented in the Brazilian continental margin, was conducted to identify the composition of both, BC and IWBC. We found that BC carries Tropical Water and South Atlantic Central Water towards south-southwest, while IWBC carries essentially Antarctic Intermediate Water and Upper Circumpolar Deep Water (UCDW) towards the north-northeast. BC has a typical thickness of 450-500m, whereas IWBC extends from the BC base to more than 1,150m deep. Typical volume transport of BC is 6Sv and of IWBC is 4Sv. The core of BC’s speeds, whose instantaneous value may reach 1m.s–1, is always located on the surface. On the other hand, IWBC’s core is between 800 and 900m and is apparently associated to the minimum salinity of the entire water column.